3 Answers
3

There are a variety of spacing techniques in math mode that you could consider. The following is taken verbatim from Herbert Voss' Mathmode document on horizontal alignment. It showcases the different types of spacing available and compares them very well:

You don't specify just how much extra space you'd like to see between the operator and its associated variable/constant, so I'll assume that it's the amount of space that would be inserted if it were a binary rather than a unary operator. In the code below, the "fake binary" operator is obtained by inserting an empty group, {}, in front of the otherwise unary operator.

Edit1:
OK, based on the Edit1 of the question, I think what the writer is after is a method for creating a "math operator," such as "\NOT", which inserts a bit of space between the operator's text and its argument. To get such an operator, insert the following text in the preamble of your document:

\newcommand{\NOT}{\ensuremath\texttt{NOT}\:}

The control sequence \: inserts a "medium space" between the NOT and the following material. Standard TeX/LaTeX methodology is to insert a "thin space" (\,) between the operator and its argument (as in \cos\theta and \det A), but in the case of an operator made up of all-uppercase letters a "thin space" does not provide quite enough separation.

If you are using the amsmath package (\usepackage{amsmath} for TeX Live) then page 15 of the User's Guide indicates that extra spacing (from least to most) is \thinspace, \medspace, \thickspace, \quad, \qquad. Negative spacing is also covered as is using symbols (such as \,) to generate equivalent amounts of space.
So the answer to your question depends on how much space you'd like.